3 files changed, 25 insertions, 0 deletions

diff --git a/arch/x86_64/Kconfig b/arch/x86_64/Kconfig
index 010d2265f1cf..5cb509dbffe4 100644
--- a/arch/x86_64/Kconfig
+++ b/arch/x86_64/Kconfig
@@ -455,6 +455,17 @@ config CALGARY_IOMMU
           Normally the kernel will make the right choice by itself.
           If unsure, say Y.
 
+config CALGARY_IOMMU_ENABLED_BY_DEFAULT
+        bool "Should Calgary be enabled by default?"
+        default y
+        depends on CALGARY_IOMMU
+        help
+          Should Calgary be enabled by default? if you choose 'y', Calgary
+          will be used (if it exists). If you choose 'n', Calgary will not be
+          used even if it exists. If you choose 'n' and would like to use
+          Calgary anyway, pass 'iommu=calgary' on the kernel command line.
+          If unsure, say Y.
+
 # need this always selected by IOMMU for the VIA workaround
 config SWIOTLB
         bool
diff --git a/arch/x86_64/kernel/pci-calgary.c b/arch/x86_64/kernel/pci-calgary.c
index 8a1e4f35bc3c..0ddf29dae7e0 100644
--- a/arch/x86_64/kernel/pci-calgary.c
+++ b/arch/x86_64/kernel/pci-calgary.c
@@ -43,6 +43,12 @@
 #include <asm/dma.h>
 #include <asm/rio.h>
 
+#ifdef CONFIG_CALGARY_IOMMU_ENABLED_BY_DEFAULT
+int use_calgary __read_mostly = 1;
+#else
+int use_calgary __read_mostly = 0;
+#endif /* CONFIG_CALGARY_DEFAULT_ENABLED */
+
 #define PCI_DEVICE_ID_IBM_CALGARY 0x02a1
 #define PCI_VENDOR_DEVICE_ID_CALGARY \
         (PCI_VENDOR_ID_IBM | PCI_DEVICE_ID_IBM_CALGARY << 16)
@@ -1061,6 +1067,9 @@ void __init detect_calgary(void)
         if (swiotlb || no_iommu || iommu_detected)
                 return;
 
+        if (!use_calgary)
+                return;
+
         if (!early_pci_allowed())
                 return;
 
diff --git a/arch/x86_64/kernel/pci-dma.c b/arch/x86_64/kernel/pci-dma.c
index f8d857453f8a..683b7a5c1ab3 100644
--- a/arch/x86_64/kernel/pci-dma.c
+++ b/arch/x86_64/kernel/pci-dma.c
@@ -296,6 +296,11 @@ __init int iommu_setup(char *p)
                 gart_parse_options(p);
 #endif
 
+#ifdef CONFIG_CALGARY_IOMMU
+                if (!strncmp(p, "calgary", 7))
+                        use_calgary = 1;
+#endif /* CONFIG_CALGARY_IOMMU */
+
                 p += strcspn(p, ",");
                 if (*p == ',')
                         ++p;